U.S. patent application number 10/058851 was filed with the patent office on 2003-07-31 for method and system for separating and sorting recyclable materials from mixed waste streams.
Invention is credited to Liddle, Franklin DeWayne, Tassielli, Ottavio Anthony.
Application Number | 20030141225 10/058851 |
Document ID | / |
Family ID | 27609689 |
Filed Date | 2003-07-31 |
United States Patent
Application |
20030141225 |
Kind Code |
A1 |
Liddle, Franklin DeWayne ;
et al. |
July 31, 2003 |
Method and system for separating and sorting recyclable materials
from mixed waste streams
Abstract
A method and system for separating and sorting recyclable
materials from mixed waste streams provides improved separation and
reduced cost in trash and recyclable material processing systems. A
low surface-current bath is used within the sorting system to
separate materials having a low wet-density, such as plastics and
coated paper, from materials having a high wet-density, such as
uncoated paper. A novel newspaper separation device using an
appropriately-sized gap in a conveying system provides separation
of newspaper from other large pieces of recyclable material or
trash, while leaving heavier materials on the conveying system for
further sorting. An improved plastics separator is included for
separating plastics by melting-point range.
Inventors: |
Liddle, Franklin DeWayne;
(Slerra Vista, AZ) ; Tassielli, Ottavio Anthony;
(Phoenix, AZ) |
Correspondence
Address: |
WEISS & MOY PC
4204 NORTH BROWN AVENUE
SCOTTSDALE
AZ
85251
US
|
Family ID: |
27609689 |
Appl. No.: |
10/058851 |
Filed: |
January 28, 2002 |
Current U.S.
Class: |
209/18 ; 209/172;
209/930 |
Current CPC
Class: |
B29L 2031/7128 20130101;
Y02W 30/622 20150501; B03B 9/06 20130101; B29B 17/02 20130101; B29B
2017/0203 20130101; Y02W 30/62 20150501; B29K 2313/00 20130101;
Y02W 30/524 20150501; B03B 5/28 20130101; B29K 2705/00 20130101;
Y02W 30/52 20150501; B29K 2711/12 20130101; B29B 2017/0255
20130101; B29B 2017/0244 20130101 |
Class at
Publication: |
209/18 ; 209/172;
209/930 |
International
Class: |
B04B 005/10 |
Claims
What is claimed is:
1. A system for sorting recyclable waste, comprising a low
surface-current bath for separating high wet-density material from
low wet-density material, wherein said low wet-density material is
conveyed across said low surface-current bath, substantially near
the surface of said low surface-current bath, and wherein said high
wet-density material submerges after entering said bath.
2. The system of claim 1, wherein said low surface-current bath
further comprises a stream generator for generating an upward
directed current within said low surface-current bath for conveying
said low wet-density material near said surface of said low
surface-current bath.
3. The system of claim 1, wherein said low surface-current bath
further comprises a n upper conveyor disposed within said low
surface-current bath and substantially near the surface of said low
surface-current bath for collecting said low wet-density material
for removal from said low surface-current bath.
4. The system of claim 3, wherein said upper conveyor comprises a
first segment and a second segment, wherein said second segment has
a first end disposed beneath a second end of said first segment,
wherein said first end of said second segment is set beneath said
second end of said second segment at a distance defining a vertical
gap between said first segment and said second segment, whereby
plastic bags are conducted through said gap to a plastics
processing system and the balance of said low wet-density material
is conveyed past said gap by said second segment.
5. The system of claim 4, further comprising a compressed air feed
directed at an angle opposing said gap, whereby said plastic bags
are further directed through said gap by said compressed air.
6. The system of claim 5, further comprising an image recognition
system disposed above said first conveyor segment an coupled to
said compressed air feed for controlling said compressed air feed
in response to recognizing plastic bags on said first conveyor
segment.
7. The system of claim 1, wherein said low surface-current bath
further comprises a lower conveyor disposed within said low
surface-current bath with a first end substantially near the bottom
of said low surface-current bath for extracting said high
wet-density material from said low surface-current bath.
8. The system of claim 1, further comprising a high surface-current
bath having an output coupled to an input of said low-surface
current bath for separating low dry-density material from high
dry-density material, wherein said low dry-density material is
conveyed across said high surface-current bath, substantially near
the surface of said high surface-current bath, and wherein said
high dry-density material submerges after entering said bath.
9. The system of claim 8, wherein said high surface-current bath
further comprises a stream generator for generating an
upward-directed current within said high surface-current bath for
conveying said low dry-density material near said surface of said
high surface-current bath.
10. The system of claim 8, wherein said high surface-current bath
further comprises an upper conveyor disposed within said high
surface-current bath and substantially near the surface of said
high surface-current bath for collecting said low dry-density
material for removal from said high surface-current bath.
11. The system of claim 10, further comprising a bar disposed above
the surface and at an angle with respect to a conveying direction
of said upper conveyor for directing plastic bottles and other
large plastic pieces to a plastics processing system.
12. The system of claim 8, wherein said high surface-current bath
further comprises a lower conveyor disposed within said high
surface-current bath with a first end substantially near the bottom
of said high surface-current bath for extracting said high
dry-density material from said high surface-current bath.
13. The system of claim 1, further comprising: a trommel for
sorting large items of recyclable material including newspaper,
textile and clothing from small items of recyclable material; a
first conveyor having a first end for receiving said large items of
recyclable material from said trommel; a second conveyor having a
first end disposed beneath a second end of said first conveyor,
wherein said first end of said second conveyor is set beneath said
second end of said first conveyor at a distance defining a vertical
gap between said first conveyor and said second conveyor, whereby
said newspaper, textile and clothing is conducted through said gap
and the balance of said large items of recyclable material is
conveyed past said gap by said second conveyor.
14. A system for sorting recyclable waste, comprising means for
separating high wet-density material from low wet-density
material.
15. A system for sorting recyclable waste, comprising means for
separating high dry-density material from low dry-density
material.
16. The system of claim 15, further comprising means for separating
high wet-density material from low wet-density material.
17. The system of claim 14, further comprising means for separating
newspapers from large items of recyclable material.
18. A method for sorting recyclable waste, comprising: receiving
mixed material containing high wet-density material and low
wet-density material; wetting said mixed material in a bath;
submerging said high wet-density material while floating said low
wet-density material; conveying said low wet-density material
across said bath, substantially near the surface of said bath to a
receiving destination for said low wet-density material; and
collecting said high wet-density material from said bath.
19. The method of claim 18, further comprising: receiving primary
mixed material containing high dry-density material and low
dry-density material; wetting said primary mixed material in a
bath; submerging said high dry-density material while floating said
low dry-density material; conveying said low dry-density material
across said bath, substantially near the surface of said bath to a
receiving destination for said low dry-density material, wherein
said receiving and wetting of said mixed material is performed on
said low dry-density material; and second collecting said high
dry-density material from said bath.
20. A system for sorting recyclable waste, comprising: a trommel
for sorting large items of recyclable material including newspaper,
textiles and clothing from small items of recyclable material; a
first conveyor having a first end for receiving said large items of
recyclable material from said trommel; a second conveyor having a
first end disposed beneath a second end of said first conveyor,
wherein said first end of said second conveyor is set beneath said
second end of said first conveyor at a distance defining a vertical
gap between said first conveyor and said second conveyor, whereby
said newspaper, textile and clothing are conducted through said gap
and the balance of said large items of recyclable material is
conveyed past said gap by said second conveyor.
21. The system of claim 20, wherein said vertical gap has a length
in the range of six inches to twelve inches.
22. The system of claim 20, wherein said second end of said first
conveyor and said first end of said second conveyor are displaced
horizontally defining a horizontal gap.
23. The system of claim 22, wherein said horizontal gap is
substantially equal to twelve inches.
24. The system of claim 20, further comprising a separator
positioned between said first conveyor and said second conveyor for
separating newspaper from said newspaper textiles and clothing,
said separator having a top edge set beneath said second end of
said first conveyor and above said first end of said second
conveyor, thereby defining a second horizontal gap between said
second end of said first conveyor and said separator and a second
vertical gap between said second end of said first conveyor and
said separator.
25. The system of claim 24, wherein said second horizontal gap is
substantially equal to three inches.
26. The system of claim 24, wherein the second vertical gap is
substantially equal to six inches.
27. A method of separating newspapers from large items of
recyclable materials, said method comprising the steps of:
receiving said newspapers mixed with said large items of recyclable
materials; conducting said received materials on a first conveyor;
further conducting said received material past the end of said
first conveyor; catching said large items of received material on a
second conveyor disposed beneath said first conveyor; and second
catching said newspaper from a gap defined by a displacement
between said first conveyor and said second conveyor.
28. The method of claim 27, wherein said method further separates
textiles and clothing from said large items of recyclable material,
wherein said second catching further catches said textiles and
clothing from said gap, and wherein said method further comprises
separating said newspaper from said textiles and clothing with a
separator defining a second gap between said first conveyor and
said separator, whereby said textiles and clothing are conducted
through said second gap and said newspapers are conducted over said
seperator.
29. A system for sorting recyclable waste including a plastic
separator for separating thermoplastic materials into collectable
fractions, said plastic separator comprising: a plurality of heated
conveyor systems for providing heated adhering surfaces, whereby
thermoplastics having a particular melting point range will adhere
to a particular one of said plurality of heated conveyor systems;
and a plurality of pinch rollers each opposing an associated one of
said heated conveyor systems for causing said particular
thermoplastics to adhere to said particular heated conveyor
system.
30. A system for sorting recyclable waste including a plastic
separator for separating thermoplastic materials into collectable
fractions, said plastic separator comprising: a plurality of heated
conveyor systems for providing heated adhering surfaces, whereby
thermoplastics having a particular melting point range will adhere
to a particular one of said plurality of heated conveyor systems;
and a plurality of preheaters for preheating said thermoplastic
materials prior to introduction to an associated one of said heater
conveyor systems, wherein each of said preheaters heats said
thermoplastic materials to a temperature approaching, but not
exceeding the temperature of said associated heated conveyor
system.
31. The system of claim 30, wherein said plastic separator further
comprises a plurality of pinch rollers each opposing an associated
one of said heated conveyor systems for causing said particular
thermoplastics to adhere to said particular heated conveyor
system.
32. A method of separating thermoplastic materials into collectable
fractions, said method comprising: preheating plastic pieces on a
conveyor to a temperature approaching but not exceeding the
temperature of a heated conveyor belt; introducing said plastic
pieces to said heated conveyor belt; scraping thermoplastic
materials that have adhered to said heated conveyor belt; and
ejecting materials that have not adhered to said heated conveyor
belt.
33. The method of claim 32, further comprising compressing said
preheated plastic pieces onto said heated conveyor belt whereby
adhesion of said plastic pieces is improved.
34. A method for removing plastic bags from a conveyor transporting
mixed recyclable materials, said method comprising: receiving said
mixed recyclable materials; conducting said received materials on a
first conveyor; further conducting said received materials past an
end of said first conveyor; catching said plastic bags from a gap
defined by a displacement between said first conveyor and a second
conveyor; and catching a remainder of said received material on
said second conveyor.
35. The method of claim 34, further comprising directing compressed
air at said gap to blow said plastic bags through said gap.
36. The method of claim 34, further comprising: recognizing said
plastic bags on said first conveyor; and controlling a flow of said
compressed air in conformity with said recognizing.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to recyclable
material processing systems, and more specifically, to a processing
system that separates and sorts recyclable materials from mixed
waste streams.
[0003] 2. Background of the Invention
[0004] The management of trash or waste in general and solid waste
in particular is a critical problem facing municipalities and
private industry today. Statistical Figures from a report issued by
the United States Environmental Protection Agency (EPA) entitled
"Municipal Solid Waste In the United States: 1999 Facts and
Figures" demonstrate the magnitude of the problem. The
above-referenced report reveals the following:
[0005] 1) In 1999, U.S. households, institutions and businesses
generated about 230 million tons of Municipal Solid Waste (MSW)
(commonly referred to as trash or garbage), which is approximately
4.7 lbs. of waste per capita per day.
[0006] 2) From 1960 to 1999 the production of MSW has increased at
a rate of 3 to 4% per year.
[0007] 3) The EPA has provided a list of preferred strategies for
handling the MSW production. Source reduction (including reuse) is
the most preferred method, followed by recycling and composting.
With disposal in combustion facilities and landfills being the
least preferred strategy.
[0008] 4) As of 1999, 28 percent of MSW in the United States was
recovered, recycled or composted, 15 percent was burned, and the
remaining 57 percent was disposed of in landfills.
[0009] 5) A typical MSW composition is:
[0010] Paper: 38.1%
[0011] Yard Waste: 12.1%
[0012] Food Waste: 10.9%
[0013] Plastics: 10.5%
[0014] Metals: 7.8%
[0015] Rubber, Leather, and Textiles: 6.6%
[0016] Glass: 5.5%
[0017] Wood: 5.3%
[0018] Other: 3.2%
[0019] Municipalities and private services provide trash collection
services for both residential and commercial customers. Typically,
most if not all of the collected trash ultimately ends up in
landfills or is incinerated, generating environmental pollution and
raising the cost of trash disposal. (Across the United States, the
percentage is over 70% according to the above-referenced
report.)
[0020] A large percentage of the total trash collected comprises
recyclable material which can be sold or otherwise more
economically dispatched, but the difficulty of separating the
recyclable material from general trash leads to diminishing returns
for the processing facility, thereby limiting the amount of
recyclable material extraction that is actually performed by the
trash processor. However, recycling is increasingly necessary and
economically efficient in light of the cost of raw materials that
could otherwise be replaced by recycled material, environmental
regulation conformance, landfill costs and the undesirability of
combustion due to the resulting atmospheric pollution and generated
heat.
[0021] Recyclable material must be separated into useful categories
for delivery to recyclable materials customers and/or on-site
processing of recyclables. Typically the categories are: glass,
plastics, paper and metals. The plastics and paper are further
separated by type and the glass may be separated by color. Plastics
must be separated due to differing compositions. Separation into
major categories of resins enables efficient reuse of the plastic
materials. Metals must also be separated into ferrous and
non-ferrous materials, and paper grades are also sorted in
categories of fiber types.
[0022] There are many forms of trash processing/recyclable
materials processing in place today. The trash collected by the
collection service provider may be pre-sorted by residential or
other customers (consumers) and collected from separate bins, but
typically there will be a percentage of non-recyclable materials
present due to improperly performed sorting or improper use of the
recyclable materials bin. The non-recyclable portion will typically
contain a large quantity of recyclable material, as the consumers
will generally not separate all of the recyclable material.
[0023] While consumer sorting is presently an important component
of the present-day waste processing systems, a consumer-sorted
system requires more cooperation by the consumers, and the system
may require more collections and collection vehicles than may be
economically practical. Therefore, not all communities may ever
implement a consumer-sorted systems and therefore have a great need
for a system that extracts and sorts recyclables directly from MSW.
Further, the broad categories of consumer-sorted recyclables must
be further sorted to produce narrower categories for further
processing and some categories such as metals may be missed
entirely by consumer-sorting schemes.
[0024] Alternatively, a collection service provider may collect the
recyclable materials mixed with trash and provide complete sorting
of recyclable materials from the general trash collected. Complete
sorting is the ultimate goal as it reduces the collection
requirements, though not necessarily the number of trips required.
Complete sorting eliminates the need to separate recyclable
materials by the consumer, thus eliminating the risk of improper
sorting. The collection service provider using a sorting requires a
more sophisticated processing system or greater human labor input
at the sorting facility. Additional labor adds to the cost of waste
disposal.
[0025] While individual systems have been developed for sorting
portions of a mixed waste stream, no comprehensive solution is
available that can efficiently separate and sort recyclable
materials from mixed waste streams. The complexity of the task and
the associated labor costs have created an obstacle to separating
recyclables from mixed collections, including both municipal solid
waste and consumer-sorted recyclables.
[0026] Therefore, it would be desirable to provide a method and
system for separating and sorting recyclable materials from mixed
waste streams. It would further be desirable to provide an method
and system that sort and separate recyclable material into useful
categories.
SUMMARY OF THE INVENTION
[0027] The above objective of providing separation and sorting of
recyclable materials from mixed waste streams is achieved in a
method and system. The method separates paper and other materials
having a high density when wet, from materials such as plastics
that have a low density when wet. A low surface-current bath is
included in the system for wetting mixed input material and
separating the low wet-density material from the high wet-density
material. The low wet-density material is conveyed across the
surface of the low surface-current bath and may be assisted by a
stream generator that generates an upward-directed current within
the bath. The high wet-density material submerges and is extracted
from a lower level within the bath. A novel newspaper removal
device is included for separating newspaper from larger trash items
using a gap sized appropriately to pass larger-sized items of trash
while permitting newspapers to fall through the gap. An improved
plastics separator is included to separate plastic by melting point
range. A novel plastics removal device is included for separating
plastic bags from a conveyor using a gap and a compressed air
stream directed at the gap. The air stream may be controlled by an
image recognition system that detects the presence of the plastic
bags.
[0028] The foregoing and other objectives, features, and advantages
of the invention will be apparent from the following, more
particular, description of the preferred embodiment of the
invention, as illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a pictorial diagram depicting a portion of a
system in accordance with an embodiment of the present
invention.
[0030] FIG. 2 is a pictorial diagram depicting further elements of
a system in accordance with an embodiment of the present
invention.
[0031] FIG. 3 is a pictorial diagram depicting yet further elements
of a system in accordance with an embodiment of the present
invention.
[0032] FIG. 4 is a pictorial diagram depicting a plastics removal
and processing system in accordance with an embodiment of the
present invention.
[0033] FIG. 5 is a pictorial diagram depicting a plastics separator
in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0034] Referring now to the figures and in particular to FIG. 1, a
portion of a recyclable material processing system in accordance
with an embodiment of the present invention is shown. Mixed
material, which may be recyclable materials combined with trash or
pre-sorted recyclable materials enter the system at the upper left
corner of the diagram. The materials may be preprocessed in a
sorting area to remove items that might otherwise cause problems in
the system.
[0035] A conveyor 14A conducts the mixed material into a rotating
cylindrical trommel 10 which has apertures sized to eject material
under a predetermined size (generally 6 to 12 inches in diameter).
The ejected material may be hand-sorted, or as depicted introduced
to an inclined shaker 16 that ejects round objects to a
hand-sorting operation. If bagged trash is to be received by the
system, a rotating spiked trommel may be used for trommel 10, where
internal spikes are welded to the inside wall of trommel 10 in
advance of the apertures, so that as bagged trash is introduced,
the bags are opened by the spikes.
[0036] Inclined shaker 16 is a conveyor tilted on an axis
perpendicular to the direction of conveyance. A shaker, which is
generally a motor or solenoid vibrator table is integrated with a
conveyor to physically vibrate the conveyor. As a result, round
items tend to move downward along the inclined axis and roll off
the inclined shaker before reaching the end of the belt. Non-round
items tend to stay on the upward side of the conveyor belt as they
move more slowly in the inclined direction and thus are generally
conveyed to the end of the conveyor for further sorting by the
portion of the system depicted in FIG. 3.
[0037] The hand sorting operation receiving the round objects from
inclined shaker 16, separates glass bottles from the remainder of
the round items. Hand sorting may be performed in a variety of
manners using conveyors, tables, bins and other arrangements to
provide for personnel safety and facilitate removal of the glass
from remaining materials. The glass bottles may be further
hand-sorted by color (or potentially sorted by an optical sensing
system). The glass bottles are then ground or crushed into an
aggregate and stored for delivery to a glass customer.
[0038] The other round objects that are ejected from inclined
shaker 16 are introduced to a magnetic sorter 18, which separates
ferrous metal items (e.g., steel cans) for delivery to a magnetic
material customer. The non-ferrous metal items mixed with other
round items are passed through an eddy current sorter 19 which
separates non-ferrous metal items (e.g., aluminum cans) for
delivery to a non-magnetic materials customer. The remaining
materials, which are generally plastic bottles are stored for
delivery to a plastics customer. The non-round items are conveyed
off inclined shaker 16 for further processing by the portion of
system depicted in FIG. 3, which is described below.
[0039] The entire above-described portion of the system that sorts
smaller objects into round and non-round objects is optional and
its use dependent on economics, including the composition of the
incoming waste and the market price for the recovered materials.
Another factor is whether or not the objects are crushed prior to
delivery, which would render the use of inclined shaker 16 less
feasible.
[0040] Larger items that were not ejected by trommel 10 are further
moved by a conveyor 14B to a second rotating cylindrical trommel 12
which generally will have larger apertures than trommel 10. A
second processing system 20 generally identical to the processing
system described above (and may share some processing paths and
elements such as the metal sorting elements described above)
processes the smaller ejected material from trommel 12. A conveyor
14C moves the material not ejected from trommels 10 and 12 to the
portion of processing system depicted in FIG. 2. The material moved
on conveyor 14C will generally be large plastic items such as
buckets and large paper items such as newspapers, cardboard and
textiles.
[0041] Referring now to FIG. 2, further elements of a recyclable
material processing system in accordance with an embodiment of the
present invention is shown. Large items not ejected by trommels 10
and 12 of FIG. 1 are conveyed by conveyor 14C to a second conveyor
24. The particular arrangement of conveyor 14C and conveyor 24
provides a newspaper, textile and clothing removal subsystem. A
displacement 25 is provided in the horizontal direction and a
second displacement 26 is provided in the vertical direction, so
that newspaper, textiles and clothing will fall through the gap
generated by the displacements, but larger pieces of cardboard and
other large items on conveyor 14C will be conducted to conveyor 24.
Without this novel mechanism, human operators are required to
manually pull newspapers, textiles and clothing from the oversized
mixed material on conveyor 14C and thus this improvement in
recyclable materials processing systems represents a significant
reduction in the cost of recyclable materials processing.
[0042] Horizontal displacement 25 is generally twelve inches, so
that most cardboard pieces will be carried forward by conveyor 24,
while most newspaper, textiles and clothing will fold and fall
under their own weight through the gap. Vertical displacement 26
may be from approximately six inches to twelve inches, to provide
room for newspapers to pass between conveyor 14C and conveyor 24 to
be collected for delivery to a newspaper customer and for textiles
and clothing to pass between conveyor 14C and conveyor 24 to be
collected for delivery to a textile and clothing customer.
[0043] A separator 27 is introduced within the above-described gaps
25 and 26 to separate newspaper from textiles and clothing. As
newspaper is generally more rigid than the textiles and clothing,
newspaper will be conducted further across horizontal gap 25 before
falling. Separator 27 removes textiles and clothing from the end of
conveyor 14C (to the left side of separator 27 for delivery to a
textile and clothing customer, and may be a divider as shown, a
chute, divided conveyor or other suitable means for conducting the
textiles and clothing. The horizontal gap 25A between conveyor 14C
and separator 27 is generally three inches and the vertical gap 26A
between conveyor 14C and the top of separator 27 is generally six
inches. The positioning of separator 27 provides that newspaper
will be conducted to the right side of separator 27 for delivery to
a newspaper customer.
[0044] Larger items that are moved past the gap onto conveyor 24
are introduced to a hammermill 27, which flattens and/or breaks the
larger items to a manageable size. The materials is then moved from
hammermill 27 by a conveyor 28 and a vacuum hood 29 is used to
extract cardboard and larger paper items from conveyor 28. The
cardboard and larger paper items are provided to a compactor 30,
which compacts the material for delivery to a cardboard customer.
The pieces of larger plastic items, metal items and other materials
that remain on conveyor 28 are reintroduced to the processing
system portion of FIG. 1 at the input of trommel 10.
[0045] Referring now to FIG. 3, processing of the non-round items
conveyed off inclined shaker 16 of FIG. 1 is depicted. Crushers 40
pulverize the material, which is introduced to a bath 44 by a
conveyor 42. Bath 44 separates low dry-density material (such as
paper and low density plastic) from high dry-density material, such
as glass, metal and high density plastic. Low density plastic
materials such as low density polyethylene (LDPE), high density
polyethylene (HDPE), polypropylene PP) and various foams will
float, while high density plastic materials such as polyethyl
tetrachloride (PET), polystyrene (PS), acetyl butastyridene (ABS),
and poly-vinyl chloride (PVC) will sink. (While HDPE is named "high
density" for the purposes of distinguishing among polyethylene
formulations in industrial use, HDPE will float in water and
therefore within the meaning of density as used to describe the
present invention, HDPE is a low density material.)
[0046] Bath 44 is a high surface-current bath designed to quickly
submerge the high dry-density material while floating the low
dry-density material toward the upper surface of bath 44 for
removal by a conveyor 48 disposed partially within bath 44. This
high surface-current may be assisted by a stream generator 46
depicted as a paddlewheel, but stream generator may be implemented
in a variety of manners, such as water jets, air jets, linear
paddle arrays or other suitable means for controlling currents
within bath 44.
[0047] Critical to operation of bath 44 is that paper (which has a
low dry-density, but a high wet-density) be conveyed out of bath 44
before it has absorbed too much water and submerges. The submerged
material in bath 44 should generally be composed of glass, metal
and high density plastics which are removed from bath 44 by
conveyors 50A and 50B (a single conveyor may be used) for
processing by a glass/metals processing system comprising a
magnetic sorter, eddy current sorter 52, and a trammel 54 for
sorting glass from other materials. Inclined shaker 16 may be
deleted from the system of FIG. 1, in which case the metals
processing system in FIG. 3 still provides an alternative path for
glass and metal sorting.
[0048] Garbage is conveyed through trommel 54 and shredded by a
shredder 58, to reduce the liquid content and produce a more
compact output for delivery to a landfill or other disposal site.
Optionally, a plastics separator (similar to that described below
for the processing of low density plastics) may be included before
shredder 58 if the volume of high density plastics at the output of
trammel 54 is sufficient to justify removing the high density
plastics before delivery to a disposal site.
[0049] Low dry-density material is removed from near the surface of
bath 44 by conveyor 48. A plastic removal and processing system 65
(which will be described in detail below) removes plastic bottles
and larger pieces of plastic from conveyor 48. The remaining low
dry-density material is introduced to a second bath 60, which sorts
low wet-density material (wood, grass cuttings, wax-coated paper,
plastic bags etc.) from high wet-density material (generally
uncoated paper). Bath 60 is similar in structure to bath 44, but is
designed with a lower surface current, so that the high wet-density
materials have time to absorb water and submerge. The high
wet-density material is removed from bath 60 by conveyors 66A and
66B (which may again be a single conveyor) and is introduced to a
compactor 68 in preparation for delivery to a paper customer.
[0050] Low wet-density material is removed from bath 60 by a
conveyor 64 disposed partially within bath 60 and substantially
near the surface of bath 60. Plastic bags are removed from conveyor
64 by plastic removal and processing system 65, and the remaining
low wet-density material (generally grass and wood that have
floated on the surface of both baths 44 and 60) is sent to shredder
58 along with the garbage left after processing the material from
the bottom of bath 44.
[0051] Bath 60 provides a novel mechanism for sorting paper from
plastics bags and other materials that will generally float
indefinitely. The surface current of bath 60 may be controlled with
a stream generator 62 which may be paddles or jets as described for
stream generator 46 within bath 44, and critical to the operation
of bath 60 is that the surface current be maintained at a
sufficiently low level that paper will absorb water and submerge
sufficiently that conveyor 64 will not extract paper and so that
paper will eventually be removed by conveyors 66A and 66B.
[0052] Referring now to FIG. 4, details of plastic removal and
processing system 65 are depicted in detail. Plastic bottles
leaving crushers 40 of FIG. 3 will generally re-expand to some
degree, as the plastic bottles have elastic memory. As described
above, plastic bottles are conveyed across the surface of bath 44
and are removed by conveyor 48. A bar 49 set at an angle (between
50 and 80 degrees) with respect to the top surface of conveyor 48
and at a height between 2 and 6 inches, is used to direct plastic
bottles and larger pieces of plastic off of conveyor 48 to a
grinder 67. The ground plastics are then sorted through a plastic
separator 69, and the plastics are stored for delivery to a
plastics customer and/or made into usable recycled material
products. A top view of the arrangement of bar 49 and conveyor 48
is depicted in callout 45.
[0053] Plastic bags and other light pieces of plastic that are
conveyed past the bar 49 are introduced to second bath 60 and are
conveyed along the surface of second bath 60 and removed by
conveyor 64. Conveyor 64 comprises two conveyor segments 64A and
64B, with conveyor 64A disposed above conveyor 64B to generate a
gap of approximately 12 inches in height. Compressed air is
introduced at an angle opposing gap by a valve/nozzle system 65,
which blows plastic bags out of the gap prior to the remaining
material reaching conveyor segment 64B. Valve/nozzle system 65 may
be a continuous air feed, a timed interval feed, or as depicted,
valve/nozzle system 65 may be controlled by an image recognizer 63
coupled to a camera 61 that identifies plastic bags present on
conveyor segment 64A and generates a signal to control valve/nozzle
system 65 (with an appropriate time delay) to blow the bags through
the gap defined between conveyor segments 64A and 64B. The plastic
bags are sent to grinder 67 for processing along with the plastic
bottles and other large plastic pieces removed from conveyor 48 by
bar 49.
[0054] Referring now to FIG. 5, the details of plastics separator
69 are depicted in accordance with an embodiment of the present
invention. U.S. Pat. No. 4,892,647, which is incorporated herein by
reference, describes a plastic separator using a three-tiered belts
system that separates plastics having differing melting points. The
plastics adhere to the belts differentially based on their melting
points, as the belts are arranged so as to progressively heat
thermoplastic materials by adhesion to the belts. The plastics are
removed by a scraper at each belt level. Various improvements to
the plastic separator described in the above-incorporated patent
application are included herein and therefore embody a novel
plastic separator.
[0055] Plastic separator 69, receives ground plastics from the
output of grinder 67 (FIG. 4). A conveyor 70 and preheater 71 are
disposed before a first heated conveyor 72 to raise the temperature
of the material on the belt to a temperature approaching or equal
to the temperature of heated belt system 72. The addition of
preheaters to the system described in the above-incorporated patent
and the separation of the three-tiered belt system into a cascaded
belt system, increases the efficiency of plastics separation
achievable in separator 69.
[0056] A pinch roller 73 is also included within heated belt system
72 to press the preheated ground plastic pieces onto the belt
within heated belt system 72, further improving operation by
improving the adhesion of plastic material to the belt within
heated belt system 72. Pinch roller 73 is maintained at a
temperature lower than that of the heated belt or alternatively is
of a material suitably selected so that the plastic material will
adhere to heated belt system 72 and not to pinch roller 73. A
scraper 74 removes the plastic chips that have adhered or melted
onto the belt of heated belt system 72, and the low melting-point
plastics are removed for recycled material use. Similarly, the next
cascaded stage comprising a preheater 71A and conveyor 76 feeding a
second heated belt system 72A removes medium melting-point
plastics. Second heated belt system 72A also includes a pinch
roller 73A. Scraper 74A removes medium melting-point plastics from
second heated belt system 72A.
[0057] Finally, a third preheater 71A and conveyor 77 introduce the
remaining material to a third heated belt system 72B, which
separates high-melting point plastics from the remaining ground
garbage. Heated belt system 72B also includes a pinch roller 73B
and scraper 74B removes high melting-point plastics from heated
belt system 72B. The material that has not adhered to any of the
belt systems 72, 72A or 72B (generally grass and wood that have
floated on the surface of both baths 44 and 60) is sent to shredder
58 along with the garbage left after processing the material from
the bottom of bath 44.
[0058] While the invention has been particularly shown and
described with reference to the preferred embodiments thereof, it
will be understood by those skilled in the art that the foregoing
and other changes in form, and details may be made therein without
departing from the spirit and scope of the invention.
* * * * *